U.S. Pat. No. 4,768,347, assigned to the assignee hereof, discloses a refrigerant recovery system that includes a compressor having an inlet coupled through an evaporator and through a solenoid valve to the refrigeration equipment from which refrigerant is to be withdrawn, and an outlet coupled through a condenser to a refrigerant storage container or tank. The refrigerant storage container is carried by a scale having a limit switch coupled to control electronics to prevent or terminate further refrigerant recovery when the container is full. The scale comprises a platform pivotally mounted by a hinge pin to a wheeled cart, which also carries the evaporator/condenser unit, compressor, control electronics, and associated valves and hoses.
There is a need for refrigerant handling equipment, including refrigerant recovery equipment of the type disclosed in the above-noted U.S. Patent, that can handle differing types of refrigerants, such as R12, R22 and R502. U.S. Pat. No. 4,939,905, also assigned to the assignee hereof, discloses such a system, including a multiple-section condenser and means responsive to refrigerant temperature and pressure at the outlet of the evaporator for automatically and selectively controlling flow of refrigerant from the compressor outlet to the individual condenser sections. However, a problem remains relative to controlling inlet flow to the evaporator and compressor for various types of refrigerant so as to maximize overall recovery speed for either liquid-phase or vapor-phase inlet refrigerant, while ensuring that refrigerant at the compressor inlet is in vapor-phase so as to prevent slugging at the compressor. Further, it is desirable to control the inlet refrigerant flow in such a way as to minimize superheating of the refrigerant in the evaporator, which reduces efficiency of the handling system and the amount of refrigerant that can be pumped therethrough.
It is conventional practice to control liquid refrigerant flow with a flow control device such as a capillary tube, an orifice tube or an expansion valve. Normally, an expansion valve can be used to control flow of a single refrigerant type, necessitating multiple valves for a system intended to be capable of handling multiple refrigerant types. A capillary tube can be employed as a compromise to control flow of multiple refrigerants having liquid feed to the inlet. A problem with each of these options, however, is that the flow control device suited for liquid flow control greatly reduces the flow rate of refrigerant vapor, which would occur the majority of the time in the case of a refrigerant recovery system, for example. A sight glass and a manual valve could be employed so that the operator could observe through the sight glass whether liquid or vapor refrigerant is flowing through the system, and manually switch refrigerant flow through a flow control device where liquid refrigerant is observed, or through a bypass line when vapor phase is observed. This option requires manual observation and control. In addition, the flow control device, such as a capillary tube, would be optimized for one type of refrigerant, but would be less than optimum for other refrigerant types where the system is intended to operate with multiple refrigerant types.
It is therefore a general object of the present invention to provide a refrigerant handling system, such as a refrigerant recovery system, that includes the capability of handling inlet refrigerant in either vapor phase, liquid phase or mixed liquid/vapor phase, that is adapted to optimize flow of refrigerant therethrough as a function of inlet refrigerant phase, that operates automatically without operator intervention, that ensures that refrigerant at the compressor inlet is in vapor phase so as to prevent slugging and possible damage to the compressor, and that is adapted for use in connection with multiple differing types of refrigerants.